The Goal Attainment Scale (GAS)
With the disease treatment landscape becoming more patient-centric, an individualized approach to evaluating a treatment intervention is of great interest to all healthcare stakeholders . One measurement tool, the GAS, allows a patient to work jointly with his/her HCP to set up individualized treatment goals. These goals may differ from patient to patient, but the goal attainment approach offers a standardized assessment of a treatment intervention in a heterogeneous group of patients [24, 25].
The GAS was first introduced in 1968 by Kiresuk and Sherman and was intended for use in the evaluation of mental health services . Since then, the GAS has been used in a broad range of healthcare and non-healthcare applications, such as mental health, education and social service, rehabilitation, randomized clinical trials in neuroscience, and geriatrics [24, 27,28,29,30].
Goal Setting and Scoring
Use of the GAS involves a semiquantitative approach, characterized by first identifying problems specific to an individual patient, and then framing these problems into goals that are specific, measurable, attainable, relevant, and time-bound (SMART) [24, 25, 31]. The HCP typically would work with his/her patient to develop treatment goals, which are then scaled using a basic evaluation design with outcomes ranging from the least to the most favorable . For example, possible values may include − 2, − 1, 0, 1, and 2, where − 2 signifies baseline performance, 0 denotes targeted performance achieved, and 2 denotes outstanding goal achievement (Fig. 1) . Each individual’s progress toward goal attainment can then be converted into a standardized T score . This method allows for assignment of a single score for a patient with multiple goals and permits comparisons between patients and between treatment modes . Thus, although GAS methodology is typically applied at an individual level to measure goal attainment, results may also be analyzed at a group level.
Implementation of GAS Methodology Across Therapeutic Disciplines
Ruble et al.  analyzed data from two randomized clinical trials that used the goal attainment approach to assess whether a parent–teacher consultation/planning framework was effective in helping children with autism meet their educational goals. Their intention was to evaluate specific assumptions about GAS scoring, comparability across groups, and whether scores were reliable and comparable when applying different behavioral observation methods. Indeed, the researchers found that scores were reliably coded and stressed the importance of study personnel practicing goal writing and development, setting goals at study onset, and testing for goal equivalency prior to study initiation to ensure methodological quality .
In an exploratory pilot study, the GAS was integrated into a work-related behavioral intervention for chronically depressed individuals with persistent work dysfunction as a way to structure the treatment intervention and track progress toward desired outcomes. Examples of desired outcomes included goals relating to work or school, such as finding a job or improving productivity, as well as health-related goals, such as weight loss or taking care of medical problems . For the majority of patients, improvements in work functioning and in the ability to meet social and interpersonal goals were realized, and the GAS was determined to be an appropriate tool for tracking individual progress toward predetermined goals .
The GAS also demonstrated utility as a primary outcome measure to assess clinically meaningful progress toward goals preset by patients/caregivers and their treating physicians in a 12-month open-label trial of donepezil hydrochloride in 108 patients with Alzheimer disease . GAS scores were shown to correlate modestly with standard outcome measures. However, the authors concluded that the GAS was most valuable when incorporating patient preferences alongside other standard measures, allowing for a broader understanding of treatment benefit .
The responsiveness of the GAS in measuring outcomes is likely related to its design, offering greater sensitivity and covering more domains than standard measures . In a randomized, double-blind trial of a specialized intervention targeted at frail, community-dwelling elderly adults, the GAS was more responsive than other standard measures of functional improvement, such as the Comprehensive Geriatric Assessment (CGA) . The GAS was able to detect differences in a patient’s function, safety, activity, and medication use that standard measures failed to capture . Furthermore, the authors maintain that the study’s randomized, double-blind design is the strongest argument against any suggestion that the GAS may be over-responsive or measures trivial changes of little clinical importance .
This small sampling of applications of the GAS approach illustrates its potential for assessing patient-desired outcomes across a range of therapeutic disciplines and practical applications.